There has been developed a technique that uses solar light and solar heat as renewable energy (JP-A-2014-6018, JP-A-2010-72549, JP-A-2013-539000, JP-A-2014-134336, JP-A-2015-14444 and E-NEXI (ISSUED IN OCTOBER, 2010), issuing body: issued and edited by Nippon Export and Investment Insurance (NEXI), General Management and Public Relations Group, Overseas group, “Solar Heat Use”).
JP-A-2014-6018 describes inventions of a metal pipe for solar light collection, a vacuum tube type solar light collection pipe, and a solar power generation apparatus.
A heat collection pipe 30 described in the paragraphs 0059 and 0060 (FIGS. 8 and 9) includes a light-selective absorbing film 12 and a glass lining layer 13. The heat collection pipe 30 includes a metal pipe 11, which is formed of a metal pipe inside of which a heating medium flows, and a glass pipe 31, which is disposed so as to cover the metal pipe 11 with a predetermined interval.
Between the metal pipe 11 and the glass pipe 31, an airtightly sealed region 33 is formed. It is described that the sealed region 33 is usually in a vacuum state of, for example, 1×10−3 Pa or less.
The fact that such double-pipe-structure heat collection pipe is applicable to solar power generation is also described in “4. Trough Solar Power Generation Facility” on p12 and p13 in E-NEXI (ISSUED IN OCTOBER, 2010).
It is described in the paragraph 0022 that while the light-selective absorbing film 12 preferably absorbs solar radiation energy efficiently, that is, absorbs light of 400 to 900 nm, the light-selective absorbing film 12 can reduce thermal radiation to the outside.
JP-A-2010-72549 describes an invention of a solar heat-combined power generation apparatus for teaching material. The paragraphs 0012 to 0015 describe the use of a wavelength-selective reflection film to separate solar light into a light component (a short wavelength side) and a thermal component (a long wavelength side).
JP-A-2013-539000 and JP-A-2014-134336 describe inventions of solar heat collectors. JP-A-2015-14444 describes an invention of a heat collection pipe (a heat collection pipe with a double-pipe structure) used to collect heat from solar heat.